Mounting structure of piston pin for hermetic compressor

ABSTRACT

The present invention relates to a mounting structure of a piston pin for a hermetic compressor. In the present invention, caulking portions  26  are beforehand formed in a connecting chamber  22  of the piston  20 , and then, a piston pin  30  is fastened to the piston  20  by means of plastic deformation of the caulking portions  26 . At this time, the caulking portions  26  are formed at upper and lower ends of an interference preventive portion  24  defined within the connecting chamber  22  and cause the upper and lower ends of the piston pin  30  to be fastened to the piston  20  within the connecting chamber  22  of the piston. According to the present invention, there is an advantage in that an outer diameter of the piston  20  is not changed during its assembling process, since the piston pin  30  can be fastened to the piston  20  merely by causing only the caulking portions  26  of the piston  20  to be subjected to the plastic deformation.

TECHNICAL FIELD

[0001] The present invention relates to a hermetic compressor, and more particularly, to a structure for mounting a piston pin, which connects a piston with a connecting rod for transforming a rotational motion of a crankshaft into a linear reciprocating motion of the piston, to the piston.

BACKGROUND ART

[0002] The interior constitution of a connecting rod type of hermetic compressor according to the prior art is shown in FIG. 1. Referring to this figure, an airtight container 1 composed of an upper container 1 t and a lower container 1 b is provided, and a frame 2 is installed within the airtight container 1. A stator 3 is fixed to the frame 2 which is in turn supported in the airtight container 1 by a spring 2S.

[0003] Further, a crankshaft 5 is installed through a central portion of the frame 2. The crankshaft 5 is integrally provided with a rotor 4, and thus, is rotated together with the rotor 4 by means of electromagnetic interaction with the stator 3.

[0004] At an upper end of the crankshaft 5, an eccentric pin 5 b is formed to be offset from a center of rotation of the crankshaft 5. In addition, a counterweight 5 c is formed at a side opposite to the eccentric pin 5 b. At a lower end of the crankshaft 5, a propeller 5 d for sucking up oil L residing at the bottom of the lower container 1 b into an oil passage 5 a formed through the crankshaft 5 is installed.

[0005] Furthermore, a cylinder 6 with a compression chamber 6′ formed therein is integrally formed in the frame 2. Further, a piston 7, which is connected to the eccentric pin 5 b of the crankshaft 5 through a connecting rod 8, is installed in the compression chamber 6′.

[0006] Here, as shown in FIG. 2, the eccentric pin 5 b is connected to a crankshaft connecting portion 8 a of the connecting rod 8, and the piston 7 is connected to a piston connecting portion 8 b of the connecting rod 8 through a piston pin 7′. A sleeve SL is press-fitted between the crankshaft connecting portion 8 a and the eccentric pin 5 b. At this time, an external surface of the sleeve SL is pressed by an inner surface of the crankshaft connecting portion 8 a so that the sleeve SL is rotated integrally with the connecting rod 8. The piston pin 7′ is connected to the piston connection portion 8 b in a state where it is press-fitted into the piston 7.

[0007] In addition, a valve assembly 9 for regulating a refrigerant introduced into and/or discharged from the compression chamber 6′ is installed at a leading end of the cylinder 6. The reference numeral 10 denotes a head cover, the reference numeral 11 denotes a suction muffler, the reference numeral 12 denotes a suction pipe for transferring the refrigerant into the airtight container 1, and the reference numeral 13 denotes a discharge pipe for discharging the refrigerant to the outside of the compressor.

[0008] In the compressor constructed as such, when electric power is applied to the compressor, the rotor 4 is rotated by means of the electromagnetic interaction between the stator 3 and the rotor 4. Simultaneously, the crankshaft 5 is rotated integrally with the rotor 4. As the crankshaft 5 is rotated, the eccentric pin 5 b offset from the crankshaft 3 (5) revolves on an axis of the crankshaft 5. The connecting rod 8 connected to the eccentric pin 5 b is interlocked with the eccentric pin 5 b to cause the piston 7 to reciprocate linearly. Thus, the piston 7 causes the refrigerant to be compressed while reciprocating linearly within the compression chamber 6′.

[0009] However, there is the following problem in the prior art mentioned above.

[0010] In general, the relationship among the connecting rod 8, the piston 7 and the piston pin 7′ is as follows. The piston pin 7′ is press-fitted into the piston 7, and the connecting rod 8 and the piston pin 7′ can be slid with each other. Therefore, the piston pin 7′ is integrally fixed to the piston 7 and performs relative motion with respect to the piston connecting portion 8 b of the connecting rod 8.

[0011] In order to produce the above motion, the piston pin 7′ should be press-fitted into the piston 7. However, as shown well in FIG. 3, the piston 7 is somewhat distorted in a vertical direction in this figure as the piston pin 7′ is press-fitted into the piston 7. Thus, a cross sectional shape of the piston does not become a perfect circle. It is a phenomenon that occurs because the piston pin 7′ is forcibly press-fitted into the piston 7.

[0012] If the piston 7 is distorted and its section does not take the shape of the perfect circle, the phenomenon occurs that uneven wear is produced on an inner wall surface of the compression chamber 6′ on which the piston 7 slides and the refrigerant leaks out between the inner wall surface of the compression chamber 6′ and the piston 7. Thus, compression of the refrigerant within the compression chamber 6′ cannot be properly made.

DISCLOSURE OF INVENTION

[0013] Accordingly, the present invention is contemplated to solve the problem in the prior art. An object of the present invention is to prevent deformation of a piston which may be produced upon connection between a connecting rod and the piston.

[0014] Another object of the present invention is to simplify an operation of connecting the connecting rod and the piston.

[0015] According to an aspect of the present invention for achieving the above objects, there is provided a mounting structure of a piston pin for a hermetic compressor, which comprises a connecting rod connected to a rotating crankshaft; a piston which linearly reciprocates by means of a rotational motion of the crankshaft transferred through the connecting rod and is formed such that a connecting chamber with the connecting rod positioned therein is opened toward a trailing end thereof; a piston pin connected to the piston within the connecting chamber in a state where it is slidably connected to the connecting rod; and caulking portions which are formed in the connecting chamber and are subjected to plastic deformation to encircle an external surface of the piston pin in order to fix the piston pin into the piston.

[0016] Preferably, the caulking portions may be formed to protrude from the piston within the connecting chamber and be provided in at least one of the locations corresponding to upper and lower ends of the piston pin.

[0017] Further, the caulking portions may be preferably formed to pair off into couples and be caulked to come into close contact with the external surface of the piston pin to fix the piston pin into the piston.

[0018] Furthermore, an interference preventive portion in which an end portion of the connecting rod slidably connected to the piston pin between the caulking portions is slidably secured may be provided in the connecting chamber.

[0019] According to the present invention constructed as such, there is an advantage in that deformation on the piston can be avoided upon fixing of the connecting rod for connecting the connecting rod and the piston.

BRIEF DESCRIPTION OF DRAWINGS

[0020]FIG. 1 is a sectional view showing the inner constitution of a general hermetic compressor.

[0021]FIG. 2 is an exploded perspective view showing the constitution of a connecting rod in a hermetic compressor according to the prior art.

[0022]FIG. 3 is an explanatory view illustrating a problem of the prior art occurring upon connection between a piston and the connecting rod.

[0023]FIG. 4 is a partial cut-away exploded perspective view showing the constitution of a preferred embodiment of a mounting structure of a piston pin for a hermetic compressor according to the present invention.

[0024]FIG. 5 is a sectional view showing the constitution of the preferred embodiment of the present invention.

[0025]FIG. 6 is a sectional view taken along line A-A′ of FIG. 5 and showing the constitution of essential components of the preferred embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0026] Hereinafter, a preferred embodiment of a mounting structure of a piston pin for a hermetic compressor according to the present invention will be described in detail with reference to the accompanying drawings.

[0027]FIG. 4 is a partial cut-away exploded perspective view showing the constitution of the preferred embodiment of the mounting structure of the piston pin for the hermetic compressor according to the present invention, FIG. 5 is a sectional view showing the constitution of the preferred embodiment of the present invention, and FIG. 6 is a sectional view taken along line A-A′ of FIG. 5.

[0028] As shown in these figures, a piston 20 for reciprocating linearly within a compression chamber 6′ is manufactured in the form of a cylinder. In a trailing end of the piston 20, a connecting chamber 22 is formed to be opened toward the rear of the piston 20. The connecting chamber 22 is a portion where a connecting rod 40 is connected to the piston 20. An interference preventive portion 24 for avoiding interference between the piston and a piston connecting portion 44 of the connecting rod 40 is formed in the connecting chamber 22. The interference preventive portion 24 is a recess formed in the connecting chamber 22, in which an end of the piston connecting portion 44 is positioned.

[0029] Caulking portions 26, to be described later, for fixing a piston pin 30 into the piston 20 are formed at the top and bottom of the interference preventive portion 24 in the connecting chamber 22. The caulking portions 26 is a part for fastening the piston pin 30 through their own plastic deformation, and are initially formed to extend toward an opening of the connecting chamber 22 as shown in a dotted line in FIG. 6. Thereafter, when the piston pin 30 is fastened into the connecting chamber 22, the caulking portions 26 are subjected to the plastic deformation through the caulking operation and then come into close contact with an external surface of the piston pin 30 as shown in a solid line in FIG. 6.

[0030] The caulking portions 26 are formed to pair off into couples, and are made such that a spacing between themselves is equal to or slightly larger than a diameter of the piston pin 30 upon manufacture of the piston 20. The caulking portions 26 do not necessarily have to be formed at positions corresponding to upper and lower ends of the piston pin 30. That is, the caulking portions 26 may be formed wherever the piston pin 30 is properly fastened.

[0031] The piston pin 30 is fixed within the connecting chamber 22 of the piston 20 by means of the caulking portions 26, and causes the connecting rod 40 and the piston 20 to be connected with each other. At this time, the piston pin 30 is fastened to the piston by means of the caulking portions 26, and slidably connected with the connecting rod 40.

[0032] Furthermore, there is provided the connecting rod 40 of which an end is connected to the crankshaft 5 and of which the other end is connected to the piston 20. The connecting rod 40 connects the crankshaft 5 to the piston 20, and transforms a rotational motion of the crankshaft 5 into a linear reciprocating motion of the piston 20. The connecting rod 40 is provided with a crankshaft connecting portion 42 for connection with the crankshaft 5 formed at the end thereof and a piston connecting portion 44 for connection with the piston 20 formed the other end thereof

[0033] Hereinafter, an operation of the mounting structure of the piston pin for the hermetic compressor according to the present invention constructed as such will be explained.

[0034] The piston 20 is generally formed through a sintering process. Thus, since the connecting chamber 22, the interference preventive portion 24, the caulking portions 26, and the like are simultaneously manufactured during the sintering process, they need not be subjected to additional machining processes.

[0035] That is, the connecting rod 40 is connected to the piston 20 merely by inserting the connecting rod 40 with the piston pin 30 inserted into the piston connecting portion 44 thereof from the trailing end of the piston 20 into the connecting chamber 22.

[0036] Then, the caulking portions 26 are subjected to the plastic deformation to encircle the upper and lower external surfaces of the piston pin 30. Consequently, the piston pin 30 is fixed to the piston 20, and can slide with respect to the piston connecting portion 44.

[0037] That is, in the process of fastening the piston pin 30 into the piston 20, the caulking portions 26, which have been formed to protrude within the connecting chamber 22, are merely subjected to the plastic deformation into a state where they can encircle the piston pin. Thus, the connection between the piston and the piston pin can be made without any influence on the external shape of the piston 20.

INDUSTRIAL APPLICABILITY

[0038] According to the mounting structure of the piston pin for the hermetic compressor of the present invention as specifically described above, since upon connection between the piston and the connecting rod, only the caulking portions are merely subjected to the plastic deformation to fix the piston pin into the piston, the shape deformation of the piston cannot be produced. Therefore, there is an advantage in that defective proportion in the process of assembling the piston can be minimized.

EXPLANATION OF REFERENCE NUMERALS TO MAJOR ELEMENTS IN THE DRAWINGS

[0039]1: Airtight container

[0040]1 b: Lower container

[0041]1 t: Upper container

[0042]2: Frame

[0043]3: Stator

[0044]4: Rotor

[0045]5: Crankshaft

[0046]5 a: Oil passage

[0047]5 b: Eccentric pin

[0048]5 c: Counterweight

[0049]5 d: Propeller

[0050]6: Cylinder

[0051]6′: Compression chamber

[0052]7: Piston

[0053]8: Connecting rod

[0054]9: Valve assembly

[0055]10: Cylinder head

[0056]11: Suction muffler

[0057]12: Suction pipe

[0058]13: Discharge pipe

[0059]20: Piston

[0060]22: Connecting chamber

[0061]24: Interference preventive portion

[0062]26: Caulking portions

[0063]30: Piston pin

[0064]40: Connecting rod

[0065]42: Crankshaft connecting portion

[0066]44: Piston connecting portion 

1. A mounting structure of a piston pin for a hermetic compressor, comprising: a connecting rod connected to a rotating crankshaft; a piston which linearly reciprocates by means of a rotational motion of the crankshaft transferred through the connecting rod and is formed such that a connecting chamber with the connecting rod positioned therein is opened toward a trailing end thereof; a piston pin connected to the piston within the connecting chamber in a state where it is slidably connected to the connecting rod; and caulking portions which are formed in the connecting chamber and are subjected to plastic deformation to encircle an external surface of the piston pin in order to fix the piston pin into the piston.
 2. The mounting structure as claimed in claim 1, wherein the caulking portions are formed to protrude from the piston within the connecting chamber, and are provided in at least one of the locations corresponding to upper and lower ends of the piston pin.
 3. The mounting structure as claimed in claim 2, wherein the caulking portions are formed to pair off into couples and are caulked to come into close contact with the external surface of the piston pin to fix the piston pin into the piston.
 4. The mounting structure as claimed in claim 2, wherein an interference preventive portion in which an end portion of the connecting rod slidably connected to the piston pin between the caulking portions is slidably secured is further provided in the connecting chamber. 